The present invention relates to a machine for measuring the moments of inertia of an artificial satellite along two axes of rotation.
The methods of measuring the moment of inertia are based on Newton's law, T=.phi.I in which I is the moment of inertia about the axis of rotation, .phi. is the angular acceleration of the satellite and T is the couple applied. As the angular acceleration .phi. is difficult to measure, most of the known machines make use of a torsional vibration applying a force or torque T proportional to the angular displacement of the satellite. Measurement of the vibration frequency or period allows the moment of inertia I to be obtained.
The known machines for measuring the moment of inertia are mainly harmonic oscillator-type machines using flexible pivots or gas bearings for determining the axis of rotation of a vibrating table upon which is fixed the satellite to be tested.
The known machines allow the absolute value of the moment of inertia relative to an axis of rotation to be measured. When it is desired to determine the moments of inertia relative to two axes of rotation, the moment of inertia relative to the axis of rotation of an artificial satellite and the lateral moment of inertia, for example, the known machines make it necessary to effect consecutive measurements while modifying the mechanical and dynamic configuration of the machine, which modifies the test conditions from one measurement to another so that these measurements are not precisely comparable.